The subject invention relates to a blocking or check valve device for preventing reverse air flow in the ventilation duct leading to the passenger space of a motor vehicle. The device includes an outer housing to which is fastened an inner frame through at least one clamp connection. Between the outer housing and the inner frame there is arranged through a clamping means at least one closing or check valve element formed of flexible, soft fabric-like sheet material. In the closed, or rest position, the sheet lies against an oblique grating. When air flow takes place, the sheet rises to an open position and engages against stay elements.
Already known in the general state of the prior art is an air return check valve or blocking device which comprises an outer housing and an inner frame provided with a closing valve. The known device is designed such that the outer housing and the inner frame are encased one in another while both elements are mutually connected by clip connections. The clip connections of the inner frame serve at the same time for fastening the whole unit into a support opening.
Also known in the state of the prior art is a return air blocking or check valve device intended to be used in motor vehicles and designed such that in order to suppress flutter noises produced by the valve element there are several hook-like stays. The stays are placed so that at the valve element height position at which fluttering begins, the valve touches the free end of at least one of the stays. This is shown in German Disclosure 3,709,244. In this known device, as air flow speed increases, the closing valve collapses in the lower edge zone and is hugged against the stays and held in angular form. This known check valve air return blocking device is connected to the associated motor vehicle support element by glue through a flange and a interposed sealing ring. Thus, in this known construction, disassembly is only possible with great difficulty. Moreover, the hook-like stays do not provide the unit with sufficient stability and rigidity.
A body design for motor vehicles is also known wherein a the ventilation system uses slits with outwardly directed flaps and corresponding hook-like surfaces. This is shown in German Disclosure 3,240,290. This known construction, however, constitutes an integral component of a vehicle body and cannot be mounted or placed onto the vehicle as a premounted unit.